The present invention relates to a socket assembly for cards, especially an assembly having multi-tiered sockets installed on a circuit board in parallel to the surface of the circuit board.
Recently, a PC card in conformity of PCMCIA standard has become widespread. The PC card is detachably installed on an electronic device, such as a personal computer, to enlarge the function of the electronic device. On the other hand, an express card is being developed to meet the recent requirements for high-speed information processing and small-sized devices. The express card is smaller than the PC card, corresponding to high-speed signals.
Considering the above-mentioned situation, where the already diffused card (PC card) and the newly diffused card (express card) are intermixed, it is preferable that a socket for the PC card and a socket for the small express card are integrally piled in a socket assembly.
The socket assembly is installed on the circuit board in the electronic device such that the cards inserted into the socket assembly are connected with the circuit board. At the present, two-tiered socket assembly is on the market. The two-tied socket assembly has a socket for the PC card in a lowest tier facing to the circuit board and a socket for the express card in an upper tier provided on the lowest tier.
Since the front openings of the two sockets are arranged at the same position, the rear end of the long socket for the PC card extends longer than that of the short socket for the express card. Each of the sockets has a terminal, which is brought into contact with the card. The terminal extends rearwardly and is bent at right angles to form a connection portion connected to the circuit board.
However, in such a conventional two-tiered socket assembly, mechanical and electrical improvements have been demanded.
That is, as mentioned above, the socket for the PC card provided in the lowest tier (hereinafter “lowest socket”), which directly faces to the circuit board, is long in the insertion direction of the card (hereinafter “card insertion direction”) and the socket for the express card provided in the upper tier (hereinafter “upper socket”) is short in the card insertion direction. Also, the openings of the respective sockets are arranged at the same position in respect to the panel of the electronic device for the convenience of the insertion of the cards. Consequently, the terminal of the upper socket extends around outside of the terminal of the lowest socket.
A mechanical problem about the conventional socket assembly is that the terminal of the upper socket becomes long, which results in a large dimension of the socket assembly in the card insertion direction. An electrical problem about the conventional socket assembly is that the long terminal makes worse the high-speed transmission characteristics required especially by the express card. If the dimension of the socket assembly in the card insertion direction is made small, the vertical portions of the two sockets, which are bent at right angles, become so close to increase the electromagnetic influences between the respective cards.